Rinko Nikaidou is a character from Yudetamago's manga and anime series Kinnikuman Nisei. She is voiced by Fumiko Orikasa. In the English dub, the character is renamed Roxanne Rock and is voiced by Lisa Ortiz.

Rinko is the adopted daughter of Mari Nikaidou and is Mantaro Kinniku's love interest. She attends Shirabara (白薔薇) Private High School, Class 2-A. In the original manga she is a kogal and debuts after the Hercules Factory Second Year Replacement Matches, but in the anime she is a more wholesome high school girl who loves wrestling and first appears during the Tel-Tel Boy fight. Her two best friends are Keiko and Tamaki Maekawa and they are almost always seen with her, although lately they have been fading into the background and she has been spending more time with Jacqueline Muscle. Although she occasionally seems more interested in Jade or Chaos, she is generally considered Mantaro's girlfriend.

She refers to Mantaro as Manta (マンタ). In the Japanese version, she and her friends refer to Seiuchin (Wally Tusket) as Sei-chan (セイちゃん).